Electromagnetic sound-producing device



Dec. 30, 1930. J VAN WAGENEN 1,786,465

ELECTROMAGNETIC SOUND PRODUCING DEVICE Filed April 24, 1928 s Sheets-Sheet 1 IHVEHTOR James H. Van Wagenen HTTO HEY Dec. 30; 1930, J. H. VAN WAGENEN ELECTROMAGNETIC SOUND PRODUCING DEVICE Filed April 24-, 1928 3 Sheets-Sheet 2 NEE-i W/ VIA VVII IHVEHTOR JOlfleS Van waqengn 1930. J. H. VAN WAGENEN ELECTROMAGNETIC SOUND PRODUCING DEVICE Filed April 24, 1928 3 Sheets-Sheet 3 mvErlTofl' James H. Van Wa enen To Source of Varying urrenfs FITTORN EY Patented Dec. 30, 1930 UNITED STATES JAMES H. VAN WAGE-NEH, OF WASHINGTON, DISTRICT OF COLUMBIA ELECTROMAGNETIC SOUND-PRODUCING DEVICE Original application filed May 10, 1923, Serial No. 638,079. Divided and this application filed April 24, 1928. Serial No. 272,535.

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This application is a division of application Ser. No. 638,079 filed on May 10, 1923.

One purpose of my invention is to provide an electromagnetic actuator having a responsive element capable of universal move- I scribed manner.

ment and which is free from mechanical stresses and strains so that its movements are due entirely to the magnetic forces created by the energizing electric currents traversing its actuating coil.

A further object of my invention is to provide an apparatus of very simple construction that will accurately respond to the varying currents in the oscillating circuits of radio receiving apparatus, although lts use is not confined to such apparatus, and is adapted to many other types of electromagnetic mechanism.

In the accompanying drawings, I have illustrated several forms in which this invention may be embodied.

Fig. 1 shows one form which is particularly adapted for use in connection with the audio amplifying circuit of a radio receiving apparatus;

Fig. 2 is a vertical sectional view on the line 2-2 of Fig. 1; v

Fig. 3 is a transverse sectional view on the line 3-3 of Fig. 2;

Figs. 4, 5', 6, 7, 8, 9, 10 and 11 illustrate various'modifications of the invention.

Electromagnetic actuatorsnniversally employ an armature which is pivoted or is otherwise held by a rigid support, so that the armature is permitted to move only in a pre- Such arrangements not only confine the armature to certain predetermined movements but also cause internal mechanical stresses therein besides creating extraneous disturbing influences. Even if the armature is suspended by a cord, it is not entirely free, being held from bodily movement in at least one direction. I have found that an armature which is subjected to internal mechanical stresses will have an acoustic periodicity of its own, which will interfere with and distort the movements or vibrations of the armature responsive to changes in the magnetic field controlling the same which varies in response to variations in the electric currents flowing in the energizing coil thereof.

In the embodiment of my invention illustrated in Figs. 1 to 3, the energizing coil 20, which is connected to the auditory circuit or to any other source of varying or intermittent currents, is held between curved plates 21 seated in recesses within the pole pieces 23 of a permanent magnet 25 and clamped by screws 24. The central space within the coil is filled by a block of any suitable elastic material 26, such as spongy rubber, cork, etc. The armature consists of a magnetizable rod 27 and is centrally held or suspended between the pole pieces by passing through the block of elastic material. Fine adjustments that may be required to accurately center the armature between the poles may be made by means ofthe iron screws 28 which constitute adjustable portions oi? the pole pieces. The elastic suspending or supporting medium permits the armature to assume its natural position free from any rigid restraint suchas would be imposed by a spring suspension and therefore without any internal mechanical stresses and to move bodily in any direction or to vibrate in any manner in response to the magnetic forces created by the energizing currents flowing in the coil 20; and at the same time said elastic suspending medium protects the armature from disturbing external influences. Moreover, it serves to absorb and prevent any tendency to natural vibrations or acoustic periodicity inherent in any part of the structure. Inasmuch as there is no fixed pivot, the lateral vibrations of the armature will oscillate about a variable center determined only by the resultant forces and which may or may not be on the central axis of the magnet; that is to say, without confining the position or location of a nodal point in the armature it is rendered aperiodically sensitive or in other words uniformly sensitive and responsive to all frequencies. The amplitude of vibration or amount of movement produced by the magnetic forces may be regulated or damped to any desired degree by adjusting the screws 30, bearing upon the disk 31, to compress the elastic medium 26.

The electromagnetic vibrations of the armature are transformed into sound waves by connecting the rod 27 to a vibratable member 35 which may be made of. paper, metal or other suitable material. Mounted on the rod 27 are adjustable clips 39 which are adapted to clamp one edge of the vibratable mem ber 35.

In the modification shown in Fig. 4, the coil 20 is held in a frame or bracket 38, secured to the upper side of the pole pieces 23 and to which the standard 36 is also attached. The armature is supported for universal movement in the blocks of elastic material 26 and 26*, the latter being clamped between plates 21 which may be adjusted laterally to center the armature by means of the clamping screws 28 and may also be compressed if desired.

In this form the armature projects below the magnet and carries an adjustable clip 39 for attachment to the sound amplifier 35.

In Fig. 5 the sound amplifying sheet is clamped to an intermediate point of the armature, one foot of the bracket 38 being omitted to permit the sheet to pass through. In the forms shown in Figs. 4 and 5, the armature moves bodily and freely in vibrating between the magnet poles.

Instead of using a flexible bowed sheet as the sound amplifier, the armature may be connected directly to the diaphragm 40 of a sound producing or amplifying horn 41 as indicated in Fig. 6.

In order that the coil may closely surround the armature, the coil 20 may be placed within a recess in the elastic cushioning medium 26, in the manner illustrated in Fig. 7.

In the arrangement shown in Fig. 8, the coil 20 is embedded in the elastic block 26 and is wound directly upon the armature. Furthermore, in this arrangement, the armature may consist of the coil alone and the iron rod 27 may be replaced by a rod of wood, brass or other light material which serves merely to transmit the vibrations of the coil to the an'lplifying sheet 35, the energizing coil 20 being thus free to vibrate in the elastic mass 26, and thereby constituting also the vibrating armature.

In Fig. 9, the actuating coil 20 is carried by the pole pieces 23 and the armature 27 is carried by the pole piece 23", thelatter being angularly adjustable by means of the screws 33. to thereby adjust the armature toward or from the pole piece 23. An arm 27 of any suitable light material attached to the armature, passes through the cushioning block 26, supported by the adjusting screw 4-6, and carries the clips 39 for attachment to the sound amplifying sheet 35.

In the arrangement shown in Fig. 10 the lower end of the armature is embedded in a block of cushioning material carried by a box 48 slidably mounted on the lower pole piece and provided with an adjusting screw 46'. I have also shown in this figure that a plurality of bowed sound creating or amplifying sheets 35 may be connected to the armature.

A further modification is illustrated in Fig. 11 in which the armature consists of the coil 20 connected to the source of varying currents, indicated conventionally by the transformer 50. The magnet may be in the form of a tubular soft iron shell 52 with an inwardly directed annular flange 53, constituting a pole piece, and a centrally disposed core 54 surrounded by the magnetizing coil 56.

The actuating coil 20, constituting the movable element, may be attached to a spool or disk 57 having a stem 58 upon which a nut 59 is threaded, for the purpose of clamping the coil to a disk 60 of elastic material, such as cork, sponge, rubber, etc. The disk 60 may be held by a sleeve 61 surrounding the magnet, the position of the coil 20 being determined by the thickness of an interposed nonmagnetic ring, rod 27 of any suitable light material is attached at an intermediate point to the end of the stem 58, the rod passing through a block 26 of elastic material and having its lower end anchored in another block 26 of elastic material. The position of the coil 20 can be adjusted by means of the screw 28. All of the parts of the moving element may be constructed of very light rnaterial which will transmit vibrations to the amplifying bowed sheet 35, in response to exceedingly feeble currents flowing in the coil 20.

I have shown the amplifying sheet attached by clip 39 directly to the actuator rod of the apparatus, but it will be evident that the free end of the sheet may be attached to a suitably supported vibratory member, which in turn is vibrated by said actuator rod. Or the amplifying sheet may be attached directly to the stem 59, the particular manner of connecting the sheet to the actuating member depending upon the degree of amplitude of vibration desired.

Having described my invention, what I believe to be new and desire to secure and protect by Letters Patent of the United States 1s 1. An electric translating device comprising a movable coil element in a magnetic field subject to mechanical impulses corresponding to sound vibrations and resilient means associated with said coil to support said coil and form a cushioning medium for the same without confining the location of a nodal point in said device.

2. An electric translating device comprising a movable coil element in a magnetic field subject to mechanical impulses corresponding to sound vibrations and resilient means directly supporting said coil in such a manner as to leave it substantially free to move in response to said mechanical impulses Without confining the position of a node in said device.

3. An electric translating device comprising movable coil element subject to mechanical impulses corresponding to sound vibrations, a sound distributing surface, means to communicate the movement of said coilto said surface, and resilient means associated With said coil and locating it irrespective of adjustment of said sound producing surface Without confining the location of a node in said device.

4. In an acoustical device the combination comprising a stationary magnet, a helix responsive to modulated current juxtaposed to the core of the magnet, resilient and compressible means for supporting said helix concentrically With respect to the core and a vibratile membrane associated with the helix and actuated thereby.

5. In an acoustical device the combination comprising a stationary magnet, a helix responsive to modulated currents juxtaposed to the core of the magnet, a resilient and compressible means forming the sole support for the helix and permitting axial movement thereof,.and a vibratile membrane associated with the helix and actuated thereby.

6. In an acoustical device the combination comprising a stationary magnet, a helix responsive to modulated currents juxtaposed to the core of the magnet, a resilient and compressible means forming the sole support for the helix and permitting axial movement thereof, means to adjust the normal position of the helix with respect to said magnet.

'i'. In an acoustical device the combination comprising a stationary magnet, a helix responsive to modulated current juxtaposed to the core of the magnet, and resilient means having substantially no natural period of vibration for supporting said helix at a normal predetermined position with respect to said core.

8. In an acoustical device the combination comprising a stationary magnet, a movable coil responsive to variations in modulated currents supported adjacent the magnet, a vibratile membrane and means to connect the coil tangentially to the membrane.

9. In an acoustical device the combination comprising a stationary magnet, a movable coil responsive to variations in modulated currents supported adjacent the magnet, a vibratile membrane and means to connect the coil to the membrane to impart tangential vibrations to at least a portion thereof.

10. In an acoustical device the combination comprising a stationary magnet, a movable coil responsive to variations in modution comprising a magnet core, a helix re-,

sponsive to modulated currents juxtaposed to the core, a tensioned poly-cylindrical sound reproducing membrane, means to connect the helix tangentially to a marginal edge of the membrane to impart vibrations tangentially of the said marginal edge.

13. A method of increasing the sensitivity of a conductor subjected to displacement under the action of a variation in current traversing the conductor comprising fioatingly mounting the member in a flexible medium in aperiodic restitution Without confining the position of the vibratory node of said member.

In testimony whereof I have afiixed my signature.

JAMES H. VAN WAGENEN. 

